Re: Poor creat/delete files performance

[Miao Xie <miaox@cn.fujitsu.com>]

On Wed, 18 Aug 2010 20:57:43 -0400, Chris Mason wrote:
> Since the files are empty, and we aren't doing enough files to trigger
> IO, it is really benchmarking the cost of the btree insertions/removals
> in comparison with ext4.  I do expect this to be higher because btrfs is
> indexing the directories twice (once by name and once by sequence number
> for faster backups).
>
> On my machine:
>
> Btrfs defaults:
>
> Create files:
> 	Total files: 50000
> 	Total time: 0.916680
> 	Average time: 0.000018
> Delete files:
> 	Total files: 50000
> 	Total time: 1.329892
> 	Average time: 0.000027
>
> Ext4:
>
> creat_unlink 50000
> Create files:
> 	Total files: 50000
> 	Total time: 0.718190
> 	Average time: 0.000014
> Delete files:
> 	Total files: 50000
> 	Total time: 0.308815
> 	Average time: 0.000006
>
> We're definitely slower than ext4, but as Ric's benchmarks show things
> tend to tilt in our favor once IO is actually done.
>
> There are two big things that would help fix this performance gap:
> Switching the extent buffer rbtree into a radix tree (esp a lockless
> radix tree), and delaying insertion of the inode so that we can do more
> in btree operations in bulk.
>
> The radix tree is a much easier and more contained project.

It is good idea, We will try to do it.

Thanks
Miao Xie